The invention relates to a pump system for delivering cryogenic liquids that consists of a storage tank for the cryogenic liquid that forms a liquid chamber and a gas chamber and at least one pump that is arranged in a container, whereby the container is connected to the storage tank in such a way that a liquid level can be adjusted in the container.
To deliver cryogenic liquids at temperatures of below xe2x88x92200xc2x0 C., to date generally one-cylinder pumps that are inserted from above into an insulating vessel are used. For reasons of installation technology, the discharge of the feeder stream is carried out via this upper pump installation opening in the insulating vessel. Filling the vessels with the media to be delivered is carried out in most cases by a large storage tank, whereby determining the maximum filling height in these vessels is found by expansion pipes (sounding pipes) or content displays. The control of the maximum filling height is carried out in most cases manually or by a contact that is triggered by the liquid, by which a solenoid valve is actuated in the gas feed or exhaust line. Since the pumps cannot be operated without sub-cooling the feeder liquid, these large-volume vessels have a pressure buildup device by which the feeder liquid can be sub-cooled within a short time.
Since especially hydrogen in liquefied form is becoming increasingly more important and motor vehicles are already operated with hydrogen, it is necessary to provide suitable pumps for refueling these motor vehicles.
The known pumps may be suitable for laboratory experiments with small feeder streams and large reliable pressure pulsations; for a quick, pulsation-free liquid refueling of motor vehicles, however, this type of pump is unsuitable. In addition, such xe2x80x9cgas station pumpsxe2x80x9d must always be ready for use (cold-start) so that by the structurally necessary compact type of design in the known pumps, an enormous flow of heat into the liquid to be delivered takes place and the liquid sub-cooling that is necessary for the function is quickly withdrawn.
The object of this invention is to make available a pump system of the above-mentioned type with which larger amounts of cryogenic liquids, especially also liquid hydrogen, can also be delivered economically and reliably.
This object is achieved according to the invention in that
a) the container is divided into two chambers (h, f), whereby one chamber (h) is arranged completely below the gas chamber of the storage tank and is connected via a liquid feed line to the liquid chamber of the storage tank, while other chamber (f) is arranged above chamber (h) and at least partially also below the gas chamber of the storage tank, whereby chamber (f) is connected via a gas return line with the gas chamber of the storage tank,
b) the induction side of the pump is connected to chamber (h), while the pressure side is connected to a discharge point provided outside of the container for discharging cryogenic liquid to a consumer,
c) chambers (h) and (f) are connected to one another via a connecting line, and
d) above the open end of the gas return line that ends in chamber (f), a gas chamber remains.
The proposed division of the container into two chambers, in connection with a gas return line, makes possible a spontaneous stabilization of the liquid level in this container, whereby the liquid in chamber (f) is always in the boiling state.
According to an especially preferred embodiment of the invention, the container is divided into chambers (h, f) by means of a pressure housing, which, on the one hand, is connected to the pressure side of the pump and, on the other hand, is connected to the discharge point that is provided outside of the container for discharging cryogenic liquid to a consumer. Suitably several, i.e., at least two, pumps are connected to this pressure housing, whereby the pressure sides of the pumps are connected to the common pressure housing. In addition, a thermal separation of chambers (h) and (f), which is also achieved by the pressure housing according to the preferred embodiment, is advantageous.
The pump is advantageously designed as a reciprocating pump with a connecting rod and spring recovery, whereby the pump pressure stroke can be implemented by exerting tensile forces on the plunger by means of the connecting rod, and the plunger can be returned to a starting position by means of springs. Several such pumps are suitably inserted in the container. Because of the possibility of individual installation and the pumps that operate on suction, the cross-sections that are relevant for heat conduction at the pumps and at the container are kept very small, by which only a very small input of heat into the container liquid is carried out. For further reduction of heat input in the container, the connecting rod is preferably brought out from the container via a seal. In the case of the especially practical solution, according to which the pump is used from above in the container, the connecting rod is brought out from the container via a heat-insulated container neck. To further reduce the gas heat conduction, an insulating cartridge can be provided in the neck of the container.
The pump system according to the invention can advantageously be used for a whole series of applications. In connection with a corresponding swash plate drive, the number as well as the diameter of the individual pumps in a common pressure housing are greatly variable, so that the pumps according to this design principle can be matched to virtually all required deliveries with minimal pressure pulsation. Because of the merits of this pump design relative to the previous design, the use of such pumps is also conceivable as an aircraft pump in the new generation of hydrogen-driven aircraft. Because of the small masses of the pump system, the cooling losses are very low. By the very simple design structure, a very reasonably priced, reliable and technically high-quality pump is made available.
Below, the invention is to be explained in more detail based on the embodiments that are depicted diagrammatically in the figures.